Core-drilling process



Jan. 22, 1929.

H. D. RINDSBERG CORE DRILLING PROCESS Filed April 1926 Far/317. 721714350119 gwventoz.

Patented Jan. 22, 1929.

UNITED" STATES 1,999,921 PATENT OFFICEQ HARRY D. RINDSBERG, OF CINCINNATI, OHIO, ASSIGNOR TO HARRY J. HATER, OF

CINCINNATI, OHIO.

CORE-DRILLIN G PROCESS.

Application filed April 2, 1926. Serial No. 99,408.

My invention relates to a method of forming wrist pin boss cores for pistons and wrist pin bosses on pistons, although not necessarily restricted to this use.

Heretofore, in the manufacture of pistons,

great difliculty has been experienced in properly centering the wrist pin boss. It has been customary to form this boss by hand, but this procedure does not insure that the boss will be correctly centered, and when the bore is drilled through the boss, one side of the boss is likely to be Weaker than the other.

An important object of my invention is to obviate these difiiculties and provide a meth- 0d whereby the boss will be molded with the piston and be properly located without subsequent centering.

Another object of my invention is the provision of a method of forming the piston cores which will form a correctly centered wrist pin boss. v

A further object of my invention is to provide an easy and inexpensive method of form ing a piston core whereby any number of pis- 2 tons may be formed w1th properly located wrist pin bosses, thereby reducing the time,

labor and expense involved in'maknig pistons and roducing a higher grade of piston.

Ot er objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings, which form a part of this specification and wherein like characters of reference denote like or corresponding parts throughout the same.

F'i duce according to my invention and showing the location of the wrist pin boss Figure 2 is a bottom lan view thereof;

Figure 3 is a side e evation of one of the core members, a fragment of the adjacent portion of the mold being illustrated in dotted lines 4 Figure 4 is a front elevation of two of the core sections with my improved reamer in operative position;

Figure 5 is a side elevation of one of the core members com leted;

Figure 6 is a ront elevation of my improved reamer, and,

' Figure 7 is an enlarged detail view thereof.

In the-drawings, wherein for the purpose of illustration is shown a preferred embodiment of my invention, the numeral 10 desigre 1 is a side elevation of a piston pro-- nates a piston having a wrist pin boss 11 arranged thereon. The bore 12 of this boss is formed by a drill not shown which is so arranged as to make the location of the bore invariable. It, therefore, becomes necessary for the boss 11 to be properly centered in order to have the bore concentric with the boss. Otherwise the walls of the boss would be thinner at one spot than at another and would consequently be materially weakened. In order to have the boss properly located in each piston I have so formed the core and mold members so as to mold the boss in its proper location, and all of the pistons produced in such a mold will be free from the disadvantages mentioned above.

The piston core comprises a plurality of core sections 13 which, when placed together form the complete core. The construction of these core sections is well known in the art and needs no explanation here. I have illustrated the form of core in which two sections form the side of the piston adjacent the wrist pin boss, half of the boss being formed by each of these sections. It is to be understood, however, that my invention may be used with other forms of cores.

In carrying out my invention I place the two core sections together, in the position shown in Figure 4 and secure them against displacement in any suitable manner. I then proceed to drill a vertical bore 14 half in one core section and half in the other, said bore being arranged exactly centrally of the point where the boss is to be located. Great care must be taken that the bore 14 is vertical. The upper end of the bore 14 is preferably enlarged, as at 15. I then insert the shaft 16 of a reamer in the bore 14' and secure the reamer head 17 to the lower end of the shaft. The shaft 16 is preferably flattened on one 95 side at 16 and is provided adjacent its lower: end with a notch 18 which is engaged by a suitable set screw 19 on the reamer head- 17, said set screw being arranged with its outer end flush'with the peripheral surface of the reamer head 17. The reamer head is cylindrical and has its upper end provided with radial cutters 20. The shaft 16 is then rotated by any suitable means and drawn upwardly, thereby cutting acylindrical opening 21 in the core sections, half of which is arranged in one section and half in the other, the shaft being positively guided by the bore 14 insuring that the opening will be properly located.

Where half of the opening is to be arranged 110 in the core sections, and half in themold section, the mold is assembled with the cores, as shown in dotted lines in Figure 3 and the opening is made in the same manner. The core sections and mold section are rigidly held together by any suitable means, to insure the proper location of the opening.

The fiat portion 16 to allow the escape of air and oil.

After the openin 21 is bored an opening 22 is formed, by d rilling, cutting or other means and this opening is plugged up as at 23. It will be seen that the filling or lug 23 serves to close the lower end of the ore 14 and may be readily shaped to form a perfect corner at 24 which is not possible by merely drilling.

It will be seen that when the core and mold sections are completed, pistons may be molded which will have properly located bosses, which will not require independent centering as has previously been the case.

While I have shown and described the preferred embodiment of myinvention, it is to be understood that various changes in the size, shape and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

Having described my invention, what I claim and desire to protect by Letters Patent is:

l. A method of forming the core of a piston mold comprising drilling a bore in said core, inserting the shaft of a reamer in said bore, and rotating the shaft to ream an opening in the core, said reamer being positively guided by the bore.

2. A method of forming the core of a piston mold comprising securing two core secof the shaft 16 serves tions of a piston mold together drilling a longitudinal bore in said core sections, a portion of said bore being arranged in each of the core sections, inserting the shaft of a reamer in said bore, and rotating the shaft to ream an opening in the core sections, said reamer being positively guided by the bore.

3. A method of forming the core of a p18- ton mold comprising securing two core sections of a piston mold together, drilling a longitudinal bore in said core sections, a portion of said bore being arranged in each of the core sections, inserting the shaft of a reamer in said bore, rotating the shaft and drawing said shaft longitudinally of the core sections to ream an opening in the core sections, said reamer"-'being positively guided by said bore, and plugging the end of the bore adjacent the opening made by the reamer.

4. A method of forming the core of a piston mold for forming a piston having wrist pin bosses thereon comprising securing two core sections and the adjacent mold section together, drilling a longitudinal bore in said core sections, a portion of said bore being arranged in each of the core sections, the bore being carefully aligned centrally of the point where the boss is to be located, inserting the shaft of a reamer in said bore, securing a reamer head to said shaft, rotating the shaft and drawing said shaft longitudinally of the core sections to ream an opening in the core sections and mold section said reamer being positively guided by said bore to properly align the opening, and plugging the end of the bore adjacent the openlng made by the reamer.

In testimony whereof I affix my signature.

HARRY D. RINDSBERG. 

